Do you have a project manager or scrum master you can chat with to make sure your UX workflow ties in properly with their Agile approach?
Having a Kanban board up somewhere public might help keep track of the status of UX suggestions, and help ‘store’ the recorded information. And making sure the user feedback is included where the team decides whether an issue has been fully addressed yet.
The most important thing is to not get bogged down in documentation when trying to communicate with others in your team. Keep it light and on-topic - sketches and chats work well for this. Work with people where you can add value and insights to their work, and try and give them quick, useful feedback without telling them how to do their job. This will hopefully also help evangelise the user-centred design approach, and help you make allies so that it’s the team who end up carrying the responsibility for UX, not just you on your own.
You do need to work out-of-sync with the rest of the dev team. The usual ways this might work for 1 week sprints is to be researching and outlining things the the week before the development sprint, and then testing and suggesting with feedback the week after. Does that sound like it would work where you are?
I know it can be overwhelming working as the sole interaction designer on multiple projects at once! Been there. =)
Make sure you’ve had a read of Jeff Gothelf’s guest blog post on this topic: http://uxmastery.com/beyond-the-basics-ux-skills-for-an-agile-world/